ELECTRON NUMBER DENSITY-FLUCTUATIONS NEAR THE PLASMAPAUSE OBSERVED BYTHE CRRES SPACECRAFT

Large quasi-periodic fluctuations in the electron number density are o ften encountered near and inside the plasmapause by the CRRES satellit e. A power spectral analysis reveals electron density fluctuations wit h frequencies ranging from 2 mHz to approximately 61 mHz. Plasma densi ty irregularities in the outer plasmasphere sometimes have power spect ral slopes near -5/3, which suggest the presence of well-developed two -dimensional magnetohydrodynamic turbulence. Quasi-periodic fluctuatio ns have been found outside the plasmasphere with spatial scales along the orbit path of approximately 750 km. A statistical analysis shows t hat the density fluctuation amplitudes are largest between L = 3 and L = 6, the region in which the plasmapause is located. The density fluc tuation amplitudes decrease with increasing L shell for L > 6. Normali zed fluctuation amplitudes greater than 10% are found in only 25% of t he available data of this study. A significant magnetic local time dep endence cannot be found due to incomplete data availability during the 9.00 to 14.99 MLT and the 15.00 to 20.99 MLT sectors.